This question comes up regularly, especially from teams trying to estimate WebSocket costs precisely:
“If I subscribe to Level 2 order book data with depth limits (for example, depth=5), is that Tier 1 or Tier 2?”
Based on CoinAPI’s pricing definitions, the answer is unambiguous:
Level 2 order book data, including depth-limited views like depth=5, is Tier 1 data.
Here’s why.
First, separate “market data level” from “pricing tier”
The confusion usually comes from mixing two unrelated concepts.
Market data levels (L1, L2, L3)
These describe market microstructure:
- L1: top of book (best bid and ask)
- L2: aggregated order book depth
- L3: order-by-order updates
Pricing tiers (Tier 1, Tier 2)
These describe how CoinAPI meters WebSocket data usage for billing.
They are not hierarchical versions of the same thing, and one does not map directly onto the other.
What Tier 1 Data means on CoinAPI
According to the pricing definition, Tier 1 Data includes:
- trades
- quotes
- order book data
Transferred from CoinAPI servers to the client via the WebSocket API.
Key characteristics of Tier 1 Data:
- measured in gigabytes (GB)
- usage resets daily
- cost per GB decreases as volume increases
- applies to raw, high-frequency market data streams
Order book data is explicitly part of Tier 1.
That means:
- Level 2 order books
- depth=5, depth=10, or full aggregated depth
All fall under Tier 1.
Depth does not change the tier.
Why depth=5 does not move data to Tier 2
Depth is a bandwidth control, not a data classification.
Requesting depth=5:
- limits how many price levels are sent
- reduces payload size
- lowers total GB transferred
But it does not change:
- the data type (order book)
- the transport method (WebSocket)
- the pricing category
You are still receiving order book data, just a smaller slice of it.
An analogy:
Reading the first five pages of a book does not turn it into a magazine. It is still the same book.
What Tier 2 Data is used for
Tier 2 Data is defined as:
- metadata
- OHLCV
- exchange rates
Transferred via the WebSocket API.
These data types:
- update less frequently
- are more compact
- are measured in megabytes rather than gigabytes
That is why they are billed separately and at different unit scales.
Importantly:
Order books are not part of Tier 2.
Practical takeaway for traders and developers
If you are using:
- Level 2 order books
- depth-limited views (for example, depth=5)
- real-time order book streams over WebSocket
Then:
- your usage is Tier 1
- your primary cost driver is GB transferred per day
- reducing depth reduces cost, but not the tier
This is exactly how the pricing model is intended to work:
optimize bandwidth without reclassifying the data.
FAQ: Tier 1 vs Tier 2 Market Data
Is Level 2 order book data considered Tier 1 or Tier 2?
Level 2 order book data is Tier 1. All order book data streamed over the WebSocket API — including depth-limited views like depth=5 - is classified as Tier 1 data.
Does using a smaller depth (e.g. depth=5) move order book data to Tier 2?
No. Depth only affects how much data is transferred, not how the data is classified. Order book data remains Tier 1 regardless of depth.
Why is order book data Tier 1 while OHLCV is Tier 2?
Tier 1 covers high-frequency raw market data such as trades, quotes, and order books. Tier 2 covers lower-frequency or derived data such as OHLCV, metadata, and exchange rates, which are billed separately and measured differently.
How is Tier 1 usage measured?
Tier 1 usage is measured in gigabytes (GB) of data transferred per day over WebSocket. Usage resets daily, and the cost per GB decreases as volume increases.
How can I reduce Tier 1 costs when using order books?
You can reduce Tier 1 usage by limiting depth, subscribing only to required symbols, and avoiding unnecessary full-book streams. These optimizations reduce bandwidth without changing the pricing tier.
Summary
- Level 2 order book data is Tier 1 on CoinAPI
- Depth controls bandwidth, not classification
- depth=5 reduces cost, not tier
- Tier 2 is reserved for OHLCV, metadata, and exchange rates
Understanding this distinction helps teams model WebSocket costs accurately and avoid unnecessary over-subscription.
If you want to explore order book streaming, depth optimization, or usage monitoring in practice, refer to the Market Data WebSocket documentation or test different depth settings to observe how they affect daily GB usage in real time.
